In known video compression systems, e.g. in MPEG, most video frames or fields are encoded in an inter-frame or inter-field mode by using e.g. discrete cosine transform (DCT) coding. To increase coding/decoding efficiency, in some video compression systems intra frame prediction is used, see MPEG-4 AVC for example.
In many video compression systems, e.g. in MPEG, every now and than a video frame is encoded in an intra-frame mode, for instance the first frame of a GOP (group of pictures) in MPEG. A GOP normally contains intra, inter or predicted, and bi-directionally predicted (I, P, B) pictures. The pictures are divided into e.g. 8*8 luminance pixel blocks or into 16*16 luminance pixel macroblocks to each of which corresponding chrominance-pixel blocks are assigned. A macroblock may represent a set of four 8*8 luminance blocks and two related 8*8 chrominance blocks. In such case the coding and the decoding is based on macroblocks and blocks.